Dissolved gas analysis devices, systems, and methods

ABSTRACT

Devices, systems, and methods for determining gas characteristics to monitor transformer operation include extracting gas from transformer fluid for analysis.

TECHNICAL FIELD

The present disclosure relates to the field of dissolved gas analysis.More particularly, the present disclosure relates to dissolved gasanalysis for transformers.

BACKGROUND

Electromagnetic devices, such as electrical transformers, can experienceelectrical inefficiencies and can generate significant heat inoperation. Abating electrical inefficiencies and removing excess heatfrom such devices can conserve operational life, performance, and reducethe maintenance needs of the devices. Fluids, such as dielectric fluids,can be used as a cooling medium to remove heat from the devices and canprovide an electrical insulation layer to suppress corona and arcing.

In operation, such cooling and/or insulating fluids can developdissolved gases. Analysis of dissolved gases within the fluids oftransformers can reveal useful information regarding the status oftransformer operation.

SUMMARY

According to an aspect of the present disclosure, a gas analysis systemfor determining characteristics of gas dissolved in a fluid of atransformer may include an extraction coil for contact with the fluid,the extraction coil including gas-permeable material for receivingdissolved gas, a gas analyzer for determining gas characteristics, thegas analyzer including a gas cell having a cavity for receiving gas foranalysis, and a gas circuit formed to include the extraction coil andthe gas analyzer to circulate gas.

In some embodiments, the extraction coil may include a number of coilloops each permitting dissolved gas to permeate therein. The gas circuitmay include a transport conduit fluidly coupled with each of theextraction coil and the gas analyzer to transport gas between theextraction coil and the gas cell for analysis. In some embodiments, thetransport conduit may include a motive pressure source fluidly coupledwith the extraction coil to circulate gas through the transport conduit.

In some embodiments, the motive pressure source may be fluidly coupledwith the extraction coil to provide a lower pressure within theextraction loop relative to a pressure within the cavity of the gascell. In some embodiments, the transport conduit may include a supplysegment fluidly connected to provide gas from the extraction loop to thegas cell. In some embodiments, the transport conduit may include areturn segment fluidly connected to provide gas from the gas cell to theextraction loop.

In some embodiments, the gas analyzer may include a light source and atleast one light detector for receiving light from the light source. Insome embodiments, the light source may be arranged to pass light fromone side of the gas cell through gas within the cavity of the gas cellto another side of the gas cell, and the at least one light detector maybe arranged on the another side to receive light from the light source.In some embodiments, the cavity of the gas cell may be arranged forreceiving dissolved gas extracted from the fluid.

In some embodiments, the gas-permeable material may include afluoropolymer. In some embodiments, the gas-permeable material mayinclude a fluoroplastic having at least one of: a yield strength withinthe range of about 26 MPa to about 29 MPa at about 73° F., a yieldstrength within the range of about 0.5 MPa to about 13 MPa at about 302°F., a yield strength within the range of about 4 MPa to about 13 MPa atabout 428° F., a tensile strength within the range of about 24 MPa toabout 29 MPa at about 73° F., a tensile strength within the range ofabout 1 MPa to about 15 MPa at about 302° F., and a tensile strengthwithin the range of about 3 MPa to about 7 MPa at about 428° F. In someembodiments, the fluoropolymer may include a fluoroplastic havingoptical transmission percent of greater than 95. In some embodiments,the fluroplastic may include a fluoroplastic having gas permeability ofat least one of H₂O of about 1142 Barrer, O₂ of about 340 Barrer, and N₂of about 130 Barrer.

In some embodiments, the extraction coil may be formed as a conduithaving an inner volume for receiving gas permeating through thegas-permeable material. In some embodiments, a gas species that is bothwithin the inner volume and dissolved in the fluid may be inequilibrium.

According to another aspect of the present disclosure, a transformer mayinclude at least one electrical winding, a fluid system including fluidfor insulating the at least one electrical winding, and a gas analysissystem for determining characteristics of gas dissolved in the fluid ofthe fluid system. In some embodiments, the gas analysis system mayinclude an extraction coil and a gas cell for analysis of gas, and theextraction coil may be arranged in contact with the fluid and includinga gas-permeable material for receiving dissolved gas from the fluid, theextraction coil and the gas cell fluidly communicating to form a gascirculation loop for circulating gas.

In some embodiments, the gas cell may be arranged for determiningcharacteristics of gas extracted from the fluid. In some embodiments, atransport conduit may be fluidly coupled with each of the extractioncoil and the gas cell to transport gas received from the fluid to thegas cell for analysis. In some embodiments, the extraction coil may beformed as a conduit having an inner volume for receiving gas permeatingthrough the gas-permeable material. In some embodiments, a gas speciesthat is both within the inner volume and dissolved in the fluid may bein equilibrium.

In some embodiments, the gas-permeable material may include afluoropolymer. In some embodiments, the gas-permeable material mayinclude a fluoroplastic having at least one of: a yield strength withinthe range of about 26 MPa to about 29 MPa at about 73° F., a yieldstrength within the range of about 0.5 MPa to about 13 MPa at about 302°F., a yield strength within the range of about 4 MPa to about 13 MPa atabout 428° F., a tensile strength within the range of about 24 MPa toabout 29 MPa at about 73° F., a tensile strength within the range ofabout 1 MPa to about 15 MPa at about 302° F., and a tensile strengthwithin the range of about 3 MPa to about 7 MPa at about 428° F. In someembodiments, the fluoropolymer may include a fluoroplastic havingoptical transmission percent of greater than 95. In some embodiments,the fluroplastic may include a fluoroplastic having gas permeability ofat least one of H₂O of about 1142 Barrer, O₂ of about 340 Barrer, and N₂of about 130 Barrer.

According to another aspect of the present disclosure, a gas analysisdevice for determining characteristics of dissolved gas of a transformermay include a gas cell defining a cavity for receiving gas for analysis,a light source arranged to transmit light, a cell light detectorarranged to receive light propagated by the light source through thecavity of the gas cell, and a reference light detector arranged toreceive light propagated by the light source through an ambient space.

In some embodiments, a cell light distance is defined between the celllight source and a reference source point of light from the lightsource. In some embodiments, the cell light distance may correspond to areference light distance defined between the reference source point andthe reference light detector. In some embodiments, the reference sourcepoint may be a beam splitter arranged to divide light from the lightsource into at least two beams, one of the at least two beams forpropagation through the cavity and another of the at least two beams forpropagation through the ambient space.

In some embodiments, the cell light detector may be arranged to receivelight from the beam propagated through the cavity that has not beenabsorbed by gas within the cavity, and wherein the reference lightdetector may be arranged to receive light from the beam propagatedthrough the ambient space that has not been absorbed by gas within theambient space. In some embodiments, each of the cell light detector andthe reference light detector may provide a signal indicating a spectrumcorresponding to light received by that detector.

According to another aspect of the present disclosure, a transformer mayinclude at least one electrical winding, a fluid system including fluidfor insulating the at least one electrical winding, and a gas analysissystem for determining characteristics of gas dissolved in the fluid ofthe fluid system, the gas analysis system including an extraction probehaving gas-permeable material for receiving dissolved gas from the fluidand a gas analyzer including at least two channels. In some embodiments,at least one of the at least two channels may be arranged to determinecharacteristics of gas extracted from the fluid.

In some embodiments, at least one of the two channels may be arranged todetermine characteristics of ambient gas. In some embodiments, the atleast two channels may be arranged to receive light propagated from thesame light source.

In some embodiments, the at least one channel may be arranged topropagate light through a gas cell containing gas extracted from thefluid for reception by a cell detector of the at least one channel. Insome embodiments, a cell light distance may be defined between areference source point of light of the light source and the celldetector. In some embodiments, the cell light distance may correspond toa reference light distance defined between the reference source pointand a reference detector of at least one other channel of the at leasttwo channels.

In some embodiments, the reference source point may include a beamsplitter arranged to divide light from the light source into at leasttwo beams, one of the at least two beams for propagation through the gascell and another of the at least two beams for propagation throughambient space. In some embodiments, the cell light detector may bearranged to receive light from the beam propagated through the gas cellthat has not been absorbed by gas within the gas cell, and wherein thereference light detector is arranged to receive light from the beampropagated through the ambient space that has not been absorbed by gaswithin the ambient space.

In some embodiments, each of the cell detector and the referencedetector may provide a signal indicating a spectrum corresponding tolight received by that detector.

In some embodiments, the gas analyzer may include a gas cell fluidlyconnected with the extraction probe to form a gas circuit. In someembodiments, the extraction probe may include an extraction coil. Insome embodiments, the extraction coil may include a number of coil turnsarranged in contact with the fluid.

According to another aspect of the present disclosure, a transformer mayinclude at least one electrical winding, a transformer fluid systemincluding fluid for insulating the at least one electrical winding, agas analysis system for determining characteristics of gas dissolved inthe fluid of the fluid system, the gas analysis system including anextraction probe having gas-permeable material for receiving dissolvedgas from the fluid and a gas analyzer including at least two channels.In some embodiments, at least one of the at least two channels may bearranged to determine characteristics of gas received from the fluid. Insome embodiments, a gas circuit may be defined at least partially by theextraction probe and the gas analyzer for circulating gas extracted fromthe fluid.

In some embodiments, the gas analyzer may include a gas cell fluidlyconnected with the extraction probe to form the gas circuit. In someembodiments, the gas analyzer may propagate light through gas within thegas cell for reception by a detector of the at least one channel.

BRIEF DESCRIPTION OF THE DRAWINGS

The concepts described in the present disclosure are illustrated by wayof example and not by way of limitation in the accompanying figures. Forsimplicity and clarity of illustration, elements illustrated in thefigures are not necessarily drawn to scale. For example, the dimensionsof some elements may be exaggerated relative to other elements forclarity. Further, where considered appropriate, reference labels havebeen repeated among the figures to indicate corresponding or analogouselements. The detailed description particularly refers to theaccompanying figures in which:

FIG. 1 is a diagrammatic view of an electrical transformer showing thatthe transformer includes a gas analysis system for determiningcharacteristics of dissolved gases within fluid of the transformer, andthat the gas analysis system includes a gas-permeable extraction probefor extracting gases from the fluid and a gas analysis module forperforming analysis on the extracted gas, and showing that theextraction probe and the analysis module are fluidly connected to form agas circuit;

FIG. 2 is an elevation view of an illustrative embodiment of a sampleportal of the electrical transformer of FIG. 1 in partial cross-sectionto show that an extraction module including the extraction probe isarranged to place the extraction probe in contact with the fluid of thetransformer;

FIG. 3 is a perspective view of an illustrative embodiment of theextraction module showing that the extraction probe is mounted on aframe to form the extraction module;

FIG. 4 is another perspective view of the extraction module of FIG. 3showing that the extraction probe is formed as an extraction coil and ismounted on a spool of the frame;

FIG. 5 is a diagrammatic view of the gas analysis module showing thatthe gas analysis module includes a gas cell containing extracted gasesand a reference space containing ambient gases, and showing that the gasanalysis module includes a light source providing a first channel formeasuring gas within the gas cell by passing a first light beam throughthe gas cell for reception by a first detector, and a second channel formeasuring gas within the reference space by passing a second light beamthrough the reference space for reception by a second detector;

FIG. 6 is a perspective view of the gas cell of the gas analysis moduleshowing that the gas cell includes windows for passing light; and

FIG. 7 is a flow diagram illustrating a process of the gas analysissystem for determining characteristics of dissolved gases within fluidof the transformer.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will herein bedescribed in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

FIG. 1 shows an illustrative arrangement of an electrical transformer 10including a gas analysis system 12 for determining characteristics ofdissolved gases within fluid of the transformer 10. The transformer 10illustratively includes a housing 14 defining an interior 16 andelectrical windings 18 arranged within the interior 16 of the housing14. The electrical windings 18 illustratively comprise windings ofelectrical wiring forming a series of turns about limbs of thetransformer 10 to produce electromagnetic effect when current is passedthrough the wiring. The transformer 10 is illustratively embodied as ahigh-voltage, three-phase, core type transformer, but in someembodiments, may include any manner of electromagnetic device includingbut not limited to shell type and/or single or multi-phase.

In the illustrative embodiment as shown in FIG. 1, the housing 14contains fluid 20 for cooling and/or electrically insulating thecomponents of the transformer 10, such as the electrical windings 18. Asmentioned above, dissolved gases can develop within the fluid 20 as aresult of operable use of the fluid 20 for cooling and/or insulation(for example, by fluid breakdown and/or faulty operational issues of thetransformer 10, generally, including leaks in the housing 14) and/or thefluid 20 may carry gases generated from the degradation of otherinsulation materials in the transformer, such as paper. The gas analysissystem 12 is illustratively arranged to extract dissolved gases from thefluid 20 for analysis.

Referring to FIG. 1, the gas analysis system 12 illustratively includesan extraction probe 22 for extracting gas from the fluid 20. Theextraction probe 22 is illustratively arranged in contact with the fluid20 and is formed of a gas-permeable material to permit permeation ofdissolved gases from the fluid 20. The extraction probe 22 isillustratively embodied as a conduit defining an interior passage forreceiving and communicating gas. The gas-permeable materialillustratively permits dissolved gases to permeate into the interiorpassage while inhibiting ingress of liquids, for example, dielectricoils. Suitable gas-permeable materials may include one or morefluoropolymers. In the illustrative embodiment, the extraction probe 22is formed as an extraction coil having coil loops in contact with thefluid 20. In some embodiments, the extraction probe 22 may include anysuitable shapes and/or forms.

As shown in FIG. 1, the gas analysis system 12 illustratively includes agas analysis module 24 for conducting analysis of gas. The gas analysismodule 24 is illustratively fluidly connected with the extraction probe22 and forms a gas circuit for circulation of gas between the extractionprobe 22 and the gas analysis module 24. An exemplary housing 25 of thegas analysis module 24 is shown in FIG. 1. The gas analysis module 24illustratively includes a gas cell 26 for receiving gas extracted fromthe fluid 20. The gas cell 26 illustratively includes a cell body 28defining a cavity 30 through which gas is passed for analysis. In theillustrative embodiment, the gas analysis system 12 conducts opticalanalysis of gas to determine gas characteristics. In the illustrativeembodiment, portions of the gas circuit other than the extraction probe22, including the cavity 30, are hermetically sealed to ambient air suchthat only the extraction probe 22 is arranged to allow permeation ofgases into and out of the gas circuit, thereby allowing gas exchangewith the transformer fluid 20.

As shown in FIG. 1, the gas analysis module 24 illustratively includes agas analysis device 32 for conducting analysis of gas within the gascell 26. In the illustrative embodiment, the gas analysis device 32 isan optical device embodied as a light spectroscopy device, namely aFourier transform infrared (FTIR) spectrometer. In some embodiments, thegas analysis module 24 may perform any manner of gas analysis techniquesand may include any suitable configuration and/or components to performsuch techniques, for example, but without limitation, ultra violet lightspectroscopy, Raman spectroscopy, photoacoustic spectroscopy, tunablediode laser absorption spectroscopy (TDLAS). The gas analysis device 32illustratively performs light spectrum analysis of gas within the gascell 26. In some embodiments, the gas cell 26 may use optical pathlength enhancement techniques such as multi-pass cells or resonantcavities. Multi-pass cells may include White cell, Herriot cell, foldedpath cells, and/or other multi-pass cells. Resonant cavities may includeFabry-Perot cavities, cavities designed for cavity ring-downspectroscopy, integrated cavity output spectroscopy (ICOS), off-axisintegrated cavity output spectroscopy (OA-ICOS), and/or other opticalpath length enhancement techniques.

As shown in FIG. 1, the gas analysis device 32 illustratively includes alight source 34 and detectors 36, 38 for receiving light from the lightsource 34. As discussed in additional detail below, the light source 34illustratively generates infrared (IR) light for propagation through gasfor observation of the light absorption characteristics of the gas. Thelight directed through the gas is received by the detectors 36, 38. Thedetectors 36, 38 are illustratively embodied as photodetectors thatreceive light propagated through gas (but that has not been absorbed bythe gas) and that generate an electrical signal indicating the lightreceived. The detectors 36, 38 are illustratively embodied as analogdetectors that generate an analog signal that is converted to a digitalsignal by an analog-to-digital converter. In some embodiments, thedetectors 36, 38 may include any suitable arrangement of signalgeneration for gas analysis.

The gas analysis device 32 illustratively determines characteristics ofthe gas based on the light received by the detectors 36, 38. In theillustrative embodiments, the gas analysis module 24 can determinecharacteristics of dissolved gas within the fluid 20 by analysis of gasextracted by the gas analysis system 12 from the transformer 10.Relevant characteristics of dissolved gases within the fluid 20 of thetransformer 10 include the presence and/or identification of such gasesand their dissolved concentrations within the fluid 20. A non-exhaustivelist of gases of interest within the fluid 20 may include, for example,oxygen (O₂), nitrogen (N₂), hydrogen (H₂), carbon dioxide (CO₂), and/orhydrocarbons (e.g., methane, ethane, acetylene, and/or ethylene), amongother gases. The gas analysis device 32 may also monitor water vapor(H₂O) extracted from the moisture dissolved in transformer oil 20.

Referring now to FIG. 2, the transformer 10 is shown in partialcross-section for descriptive purposes. The housing 14 of thetransformer 10 illustratively includes a sampling portal 40 defining aportion of the interior 16 containing fluid 20 as part of the housing14. The sampling portal 40 illustratively includes pipe extension 42connected with a wall 43 of the transformer 10 and a shroud 44 securedwith the pipe extension 42. The extraction probe 22 is illustrativelymounted within the shroud 44 in contact with fluid 20. The extractionprobe 22 is illustratively mounted within a fluid chamber 46 defined bythe shroud 44 as a part of the interior 16. The chamber 46illustratively contains fluid 20 as part of the housing 14 and fluidlycommunicating through the pipe extension 42. In the illustrativeembodiment, the pipe extension 42 illustratively includes a valve 48disposed fluidly between the wall 43 and the chamber 46 to permitisolation of the extraction probe 22, but in some embodiments, the valve48 may be excluded. In some embodiments, the extraction probe 22 may bearranged inside of the wall 43.

The gas analysis system 12 illustratively includes an extraction module50 as shown in FIGS. 2-4. The extraction module 50 illustrativelyprovides a packaging platform for mounting the extraction probe 22within the housing 14 as shown in FIG. 2. Referring to FIGS. 3 and 4,the extraction module 50 illustratively includes a mounting frame 52 andthe extraction probe 22 secured with the mounting frame 52. In theillustrative embodiment, a pump 54 is mounted to the frame 54 and isfluidly connected with the extraction probe 22 to provide a motivepressure source for circulation of gas within the gas circuit. Controlvalves and/or other flow distribution devices for operation of the gascircuit may be mounted to the mounting frame 52.

As shown in FIGS. 3 and 4, the mounting frame 52 illustratively includesan engagement wall 56 and a probe arm 58 extending from the engagementwall 56. The engagement wall 56 illustratively includes a face 60 thatforms at least a portion of fluid boundary of the chamber 46. Theengagement wall 56 illustratively supports the probe arm 58 forextension within the chamber 46 for contact with fluid 20.

In the illustrative embodiment as shown in FIGS. 3 and 4, the probe arm58 includes a spool 62 having the extraction probe 22 (embodied as anextraction coil) looped around the spool 62. In the illustrativeembodiment, the extraction coil is looped around the spool 62 to form anumber of coil turns having a successively stacked arrangement forexposure to fluid 20. Increasing the number of coils may improve theeffective exchange surface between oil and gas phase and may reduce theresponse time of the measurement. Gas circulated through the extractionprobe 22 portion of the gas circuit illustratively flows successivelythrough each of the coil turns and out for circulation to the gasanalysis device 32. In the illustrative embodiment, the extraction probe22 is fluidly connected with the pump 54 for communication of extractedgas through the gas circuit.

As best shown in FIG. 4, the spool 62 is illustratively cantileveredfrom the engagement wall 56 and provides structure for arranging theextraction probe 22 for contact with fluid 20. In some embodiments, theextraction probe 22 may be secured to the mounting frame 52 in anysuitable manner and/or arrangement. The spool 62 is illustrativelyformed as a structural frame defining an annular spool bed 61 forreceiving the extraction probe 22 wrapped thereon and defining openings63 extending through the spool bed 61 to permit fluid 20 to contactinterior portions of the extraction probe 22 to increase the effectiveexchange surface between oil and gas phase. The spool 62 isillustratively shaped as a hollow cylinder to permit fluid 20 therein.The spool 62 illustratively includes a strut 65 bridging radially acrossthe spool bed 61 to provide structural support and defining openings 67to permit circulation of fluid 20 through the spool 62.

Returning briefly to FIG. 1, as previously mentioned, the extractionprobe 22 and the gas analysis module 24 are fluidly connected to definea gas circuit for circulation of gas therebetween. In the illustrativeembodiment, the extraction probe 22 and the gas analysis module 24 arefluidly connected by transport conduit 64 including conduit segments 66,68. The segment 66 is illustratively embodied as a supply segment forproviding gas from the extraction probe 22 to the gas analysis module 24and the segment 68 is embodied as a return segment for providing gasfrom the gas analysis module 24 to the extraction probe 22.

In the illustrative embodiment, the pump 54 is arranged fluidly alongthe supply segment 66 and provides a lower pressure level at the outputof the extraction probe 22 (relative to the pressure of the gas cell26), which may assist with extraction of dissolved gases. In someembodiments, the gas circuit may be formed substantially or entirely bythe extraction probe 22 and gas analysis module 24 being fluidlyconnected with each other by direct connection and/or with little or notransport conduit 64. In some embodiments, the extraction probe 22 andgas analysis module 24 may be partly or wholly combined into a commonmodule and/or arranged within a common housing for compact arrangement.

The gas circuit illustratively provides a circulation loop forcommunication of gas between the extraction probe 22 and the gasanalysis module 24. In the illustrative embodiment, the gas circuitencourages the gas extracted from the fluid 20 to reach and maintainequilibrium with dissolved gases within the fluid 20. Such passiveextraction and non-destructive analysis can avoid practical challengeswith active sampling, such as fluid leaks, contamination, and wastematerials, among others. Passive extraction does not rely on a precisedetermination of the extraction rate of the gas and thus reduces theneed for factory calibration of each analyzer extraction rate. Asmentioned above, the pump 54 illustratively assists circulation of thegas through the gas circuit and may assist extraction, but in someembodiments, circulation of the gas through the gas circuit may beprovided by any suitable device(s), including but not limited toredundant pumps arrangements or arrangements without a pump such asconvective and/or diffusive transport.

Referring now to FIG. 5, a diagrammatic illustration of the gas analysismodule 24 is shown. As mentioned above, the gas analysis module 24illustratively includes the gas analysis device 32 arranged forconducting analysis of gas within the gas cell 26. The light source 34of the gas analysis device 32 illustratively includes a light generationsource 70. In the illustrative embodiment, the light generation source70 includes an interferometer for modulating mid-IR light, for example,with a wavelength within a range of about 1 microns to about 50 microns(in some illustrative embodiments), about 2.5 microns to about 25microns (in other illustrative embodiments), and about 2.5 to about 16microns (in still other illustrative embodiments). The light generationsource 70 also illustratively includes at least one light generator 72for generating the mid-IR light and may include various relays, filters,and/or other conditioning devices (collectively indicated as 74) forproviding suitable light for gas analysis. A non-limiting example of asuitable light generator 72 may include a glow bar (globar). The lightsource 34 illustratively includes a relay mirror 76 arranged to receivea beam of light 78 from the light generation source 70 and a beamsplitter 80 arranged to receive the beam 78 from the relay mirror 76.

As shown in FIG. 5, the gas analysis device 32 illustratively includestwo optical channels as explained herein. The beam splitter 80illustratively divides the beam 78 into two beams of light 82, 84 forspectrum analysis. The beam splitter 80 is illustratively embodied tohave a beam-splitting ratio of 50:50 (50/50 splitter) dividing the beam78 evenly into the two beams 82, 84, but in some embodiments, the beamsplitter 80 may have other suitable beam-splitting ratios. In someembodiments, any suitable arrangement of relays, filters, splitters,and/or other conditioning devices may be employed to propagate lightaccordingly for gas analysis. Beams 82, 84 propagate through respectivedefined spaces for collection by detectors 36, 38.

In the illustrative embodiment as shown in FIG. 4, analysis of the beams82, 84 propagated through respective defined spaces can determinecharacteristics of the gas extracted from the fluid 20. The beam 82illustratively propagates through the gas cell 26 for reception bydetector 36. The beam 82 illustratively enters the gas cell 26 through awindow 86, propagates through the cavity 30 for interaction with gastherein, and exits the gas cell 26 through another window 88. Light fromthe beam 82 exiting the gas cell 26 is received by the detector 36 foranalysis. The gas within the cavity 30 affects the beam 82 in a mannersuch that the affected light received by detector 36 can indicatecharacteristics of the gas within the cavity 30. As explained below, thedetector 36 can generate a signal related to the absorption spectrum ofthe gas within the cavity 30 based on the light received from beam 82.

In the illustrative embodiment, the gas within the cavity 30 absorbsenergy from the beam 82 in the form of electromagnetic radiation. Theremaining energy of beam 82 passes through the gas and is received bythe detector 36 to generate a signal related to an absorption spectrumin the illustrative embodiment. The absorption spectrum of the relevantgas can include the fraction of incident radiation absorbed by the gassample (in this instance, the gas within the cavity 30) over a range ofwavelengths and/or frequencies of propagated light. By analysis of thelight received by the detector 36 (for example, but without limitation,the wavelength and/or frequency thereof), the characteristics of the gaswithin the cavity 30 can be reliably determined. Moreover,characteristics of the dissolved gases within fluid 20 can be determinedbased on the characteristics of the gas within the cavity 30. In someembodiments, other analytical techniques and/or equipment may be used todetermine gas characteristics. In some embodiments, additional gasanalysis devices may be included in the gas cell to detect certaingases, such as hydrogen (H₂), oxygen (O₂), and/or nitrogen (N₂), andsome of those additional gas analysis devices may use non-opticalmeasurement principals that do not require gas interaction with light,such as resistive, capacitive, and/or thermo-conductive sensors, by wayof example.

Accurate determination of the characteristics of gas within the cavity30 (and ultimately the dissolved gases within fluid 20) should accountfor contaminants and/or artifacts. Common sources of artifacts includesconstituents within the air contained in the gas analysis module 24and/or constituents within the air in the vicinity of the transformer 10that may enter the gas analysis module 24. For example, ambient airwithin the gas analysis module 24 can reduce the light received by thedetector 36 even though it cannot enter into the cavity 30. Accordingly,reference information regarding the ambient environment can be useful ininterpreting the light received by the detector 36. In the presentdisclosure, the terms “air” and “ambient air” are not intended to limitthe gas constituents which can be considered, but may include any gasconstituent, including constituents of the same species as the dissolvedgases of interest in the fluid 20. By considering such referenceinformation of ambient air, the characteristics of the gas within thecavity 30 (and by correspondence, the characteristics of the dissolvedgases within the fluid 20) can be accurately determined by correctionand/or calibration of the light received by the detector 36 (absorptionspectrum). Such corrective approaches can reduce the need for purging,scrubbing, desiccants, relay adjustment, and/or other resource-laden ormechanically demanding techniques to achieve accurate results.

As shown in FIG. 5, the beam 84 (split from the beam 82) illustrativelypropagates through a reference space 90 to provide characteristics ofambient air as reference information. The reference space 90illustratively contains ambient gas (illustratively embodied as ambientair) which affects the beam 84 in a manner such that the affected lightreceived by detector 38 can indicate characteristics of the ambient gas.The characteristics of the ambient gas can be used in interpreting thelight received by detector 36. Analysis of the light received by thedetector 36 in combination with the light received by the detector 38can allow determination of characteristics of the gas within the cavity30 (and, hence, the characteristics of the dissolved gases within thefluid 20) by reducing artifacts from the light absorbed by the ambientgas. Reduction of artifacts from the light absorbed by the ambient gasis illustratively achieved by consideration of the correspondingabsorption spectra perceived by detectors 36, 38. In some embodiments,reference information may be obtained by any suitable technique and/orequipment.

In the illustrative embodiment as shown in FIG. 5, the beam splitter 80effectively provides a reference source point 92 for propagation oflight through the defined spaces 30, 90. The reference source point 92is illustratively represented as a single point on the beam splitter 80for descriptive purposes. As shown in FIG. 5, a propagation distanced_(i) is illustratively defined between the reference source point 92and each of the detectors 36, 38. A first propagation distance, referredto as a cell distance d_(cell), is illustratively defined between thereference source point 92 and the detector 36. The cell distanced_(cell) illustratively corresponds to the propagation of the beam 82. Asecond propagation distance, referred to as a reference distanced_(Ref), is illustratively defined between the reference source point 92and the detector 38. The reference distance d_(Ref) illustrativelycorresponds to the propagation of the beam 84. A third propagationdistance, referred to as the cell body distance L, is illustrativelydefined between the first window 86 and the second window 88 delimitingthe cavity 30 of the gas cell 26. In the illustrative embodiment, thedistance resulting from the subtraction of the cell body distance L fromthe cell distance d_(cell) is substantially equal to the referencedistance d_(Ref) in such a way that the propagation distances in ambientair between the reference source point 92 and each of the detectors 36,38 are substantially equal. In other embodiments, however, thepropagation distances in ambient air between the reference source point92 and each of the detectors 36, 38 may be different from each other anda correlation can be applied to equate their corresponding absorptionspectra.

In the illustrative embodiment, the light source 34 provides the beam oflight 78 for division into beams 82, 84 for respective propagationthrough each of the cavity 30 and reference space 90. Thus, the lightsource 34 illustratively provides each of beams 82, 84 simultaneouslyfrom the same source for use in two optical channels; one channelanalyzing light propagated through the gas cell 26, and another channelanalyzing light propagated through the reference space 90. The dualchannel arrangement using the same source of light can promoteuniformity between the spectral characteristics of the channels anddecrease adjustable parameters (e.g., moving optics,pressure/temperature modulation of gas samples) and/or the use ofcommodities (e.g., purge gas, desiccants, scrubbers) in obtainingreliable readings.

Devices, systems, and methods of the present disclosure can beadvantageous for remote operation where commodities and/or maintenanceavailability is of concern. Moreover, arrangements of the presentdisclosure can account for unexpected and/or unknown contaminants, evenwithout identifying the exact contaminant. In some embodiments, thereference information of the ambient gas may not identify one or more ofthe substances in the gas analysis module 24 and/or located between thelight generator 72 and detectors 36, 38. However, the referenceinformation of the unidentified substance can still be considered inaccurately determining the characteristics of the gas within the cavity30.

Referring now to FIG. 6, an illustrative embodiment of the gas cell 26is shown. The gas cell 26 illustratively includes a housing 94, which isshown partially cutaway (and semi-transparent) to reveal a cell body 96that defines the cavity 30 therein (the cell body 96 being anillustrative embodiment of the cell body 28 of FIG. 1). The cell body 96illustratively includes openings 98 penetrating through the cell body 96on opposite ends 100, 102 to connect with the cavity 30. Each opening 98is enclosed by a respective one of the windows 86, 88. The cell body 96illustratively includes gas ports 104, 106 that each penetrate throughthe housing 94 and fluidly connect with the cavity 30 to form a portionof the gas circuit to communicate gas with the extraction probe 22.

The gas port 104 is illustratively embodied as an inlet port (relativeto the gas cell 26) for receiving gas from the extraction probe 22 andthe gas port 106 is embodied as an outlet port for sending gas to theextraction probe 22. The cell body 96 illustratively includes pressureand temperature sensor ports 108 for insertion of pressure andtemperature sensors 122, 124 (shown in FIG. 1) to monitor the conditionswithin the cavity 30. A cell heater 110 including electrical leads 111is illustratively connected with the cell body 96 within the housing 94to provide temperature control of the cavity 30.

Referring to FIG. 7, an illustrative flow diagram is shown. A process200 for determining characteristics of gases is described relative toboxes 202-208. In box 202, dissolved gases are illustratively extractedfrom fluid 20 of the transformer 10. In the illustrative embodiment, thedissolved gases are extracted by permeation into the extraction probe 22to enter the gas circuit. The process illustratively proceeds from box202 to box 204.

In box 204, extracted gas illustratively enters a detection field. Inthe illustrative embodiment, the extracted gas enters the detectionfield as it circulates through the gas cell 26 and light is propagatedthrough the extracted gas for reception by the detector 36. Inembodiments in which reference information is used for correction, inbox 206, the characteristics of ambient gases are detected. In theillustrative embodiment, the second channel of the gas analysis module24 propagates light through the reference space 90 and the ambient gastherein for reception by the detector 38. The process proceeds from box204 to box 208.

In box 208, gas within the detection field circulates out of thedetection field. In the illustrative embodiment, gas within the gas cell26 is circulated through the gas circuit to return to the extractionprobe 22. The circulation of the gas within the gas circuit promotesnon-destructive testing and enables equilibrium between gas in the gascircuit and dissolved gas within the fluid 20.

Returning briefly to FIG. 1, operation of the gas analysis system 12 andthe various methods and functions described herein is illustrativelygoverned by a control system 112. The control system 112 illustrativelyincludes a processor 114, memory device 116, and communicationscircuitry 118 in communication with each other. The memory device 116stores instructions for execution by the processor 114 to conductoperations of the gas analysis system 12. In the illustrativeembodiment, the instructions include at least one algorithm forconducting the disclosed operations, but in some embodiments, theinstructions may include any of look up tables, charts, and/or otherreference material. The communications circuitry 118 illustrativelyincludes various circuitry arranged to send and receive communicationsignals between the control system 112 and various components asdirected by the processor 114. It will be appreciated that thecommunications circuitry 118 also allows the control system 112 tocommunicate with other devices, including remote devices, and alongvarious communications networks, such that the gas analysis system 12(as well as the transformer 10) can be connected to and form part of theInternet of Things. As a result, various components of the gas analysissystem 12 may be sensed and/or controlled remotely across existingnetwork infrastructure.

The control system 112 is illustratively arranged in communication withthe gas analysis module 24 and the pump 54 through communication links120 to communicate signals to govern their operation. Communicationlinks 120 illustratively include hardwired connections, but in someembodiments may include any of hardwired and wireless connections,and/or combinations thereof. In the illustrative embodiment, the controlsystem 112 is in communication with each of the light source 34, thedetectors 36, 38, gas cell temperature and pressure sensors 122, 124through individual links 120, but in some embodiments, the controlsystem 112 may be in communication with components of the gas analysismodule 24 by one or more shared links 120. The control system 112illustratively performs spectrum analysis of the light received by thedetectors 36, 38 and determines the characteristics of the gas withinthe cavity 30 and the corresponding characteristics of the dissolved gaswithin the fluid 20.

As shown in FIG. 1, the transformer 10 illustratively includes a pump126 arranged to circulate fluid 20 within the housing 14. Circulatingthe fluid 20 can assist in providing uniform distribution of dissolvedgases and can assist in extracted gases reaching accurate equilibriumfaster than with stagnant fluid conditions. In the illustrativeembodiment, the pump 126 is a thermal pump circulating the fluid 20 byconvective movement. In other embodiments, any suitable device forcirculating the fluid 20 may be used, including, for example, adisplacement pump and/or an agitator. In the illustrative embodiment,the control system 112 is in communication with the pump 126 to governoperation of the pump 126.

In the illustrative embodiment, the control system 112 is embodied togovern operations of all components of the gas analysis system 12. Insome embodiments, the control system 112 may govern operation of othersystems of the transformer 10. In some embodiments, the control system112 may include multiple processors, memory devices, and/orcommunications circuitry that may have any suitable arrangementincluding but not limited to dedicated and partly or wholly sharedarrangements. In some embodiments, another control system 112 may bededicated to govern operation of the gas analysis module 24 and theremainder of the gas analysis system 12 may be governed by the controlsystem 112.

As mentioned above, the extraction probe 22 may include a suitablepermeable material, for example, fluoropolymers. Suitable gas-permeablematerials may include, for example, but without limitation, amorphousfluoroplastics. such as Teflon® AF and/or Chemours® AF, as marketed byProfessional Plastics, Inc. (under affiliation and/or with permissionfrom DuPont®), with typical properties as shown in the table below:

Typical Properties of Teflon ® AF Optical Clarity Clear: >95% Upper UseTemperature, ° C. (° F.) 285 (545)     Thermal Stability, ° C. (° F.)360 (680)     Thermal Expansion (linear), ppm/° C. 80 Water Absoption NoWeatherability Outstanding Flame Resistant LOI, % 95 Tensile Modulus,Mpa (psi) 950-2150 (137, 786-311, 832) Creep Resistance Good SolubilitySelected solvents Resistence to Chemical Attack Excellent Surface-FreeEnergy Low Refractive Index 1.29-1.31 Dielectric Constant 1.89-1.93

Non-limiting examples may include Teflon® AF 1600 and/or Teflon® AF 2400(and/or Chemours® AF 1600 and/or AF 2400) having typical properties asdescribed within the table below:

Typical Property Data for Teflon ® AF Amorphous Fluoroplastics ASTMGrade Property Method Unit 1600 2400 Electrical Dielectric Constant D1501.93 1.90 Dissipation Factor D150 0.0001-0.0002 0.0001-0.0003 DielectricStrength D149 kV/0.1 mm 2.1 1.9 Optical Optical Transmission D1003% >95 >95 Refractive Index D542 1.31 1.29 ABBE Number 92 113 MechanicalYield Strength MPa 23° C. (73° F.) 27.4 ± 1.0  26.4 ± 1.9  150° C. (302°F.) 6.7 ± 5.9 220° C. (428° F.) 8.7 ± 4.0 Tensile Strength D638 MPa 23°C. (73° F.) 26.9 ± 1.5  28.4 ± 1.9  150° C. (302° F.) 7.7 ± 6.1 220° C.(428° F.) 4.2 ± 1.8 Elongation at Break D638 % 23° C. (73° F.) 17.1 ±6.0  7.9 ± 2.3 150° C. (302° F.) 89.3 ± 13.1 220° C. (428° F.) 8.4 ± 4.1Tensile Modulus D638 GPa 1.6 1.5 Flexural Modulus D790 GPa 23° C. (73°F.) 1.8 ± 0.1 1.6 ± 0.1 150° C. (302° F.) 1.0 ± 0.1 220° C. (428° F.)0.7 ± 0.1 Hardness Rockwell D785 23° C. (73° F.) 103 97.5 DurometerD1706 Shore D 23° C. (73° F.) 77 75 150° C. (302° F.) 220° C. (428° F.)70 65 Impact Strength Notched Izod N — — Deflection Temperature  (66psi) D648 ° C. (° F.) 156 (313) 200 (392) (264 psi) 154 (309  174 (345)Chemical Contact Angle with Water D570 Degrees 104 105 Critical SurfaceEnergy Dynes/cm 15.7 15.6 Taber Abrasion cc/2000 cycles 0.107 0.2Chemical Resistance Water Absorption % <0.01 <0.01 Gas Permeability H₂OBarrer 1142 4026 O₂ Barrer 340 990 N₂ Barrer 130 490 CO₂ Barrer 2800Other T_(g) D3418 ° C. (° F.) 160 (320) ± 5 240 (464) ± 10 SpecificGravity D792 1.78 1.67 Melt Viscosity D3835 Pa s 2657 540 at 250° C.,100 s⁻¹ at 350° C., 100 s⁻¹ Volume Coefficient of E831 ppm/° C. 260 301Thermal Expansion

In some embodiments, any suitable materials for gas-permeable,liquid-resistant extraction of dissolved gases from transformer fluidmay be applied.

The present disclosure includes devices, systems, and methods for oiland gas management for dissolved gas analyzers for use in transformermonitoring. The devices, systems, and methods of the present disclosuremay include detecting dissolved gases in insulating oil of electricalequipment using gas equilibrium theory. Equilibrium can be achievedrelative to the solubility of a gas in a transformer fluid 20, such asmineral oils, ester-based oils, or other insulation fluids, at a giventemperature and for a given partial vapor pressure of a gas. Gassolubility can be described with quantities such as Ostwald coefficientsof gas solubility that are specific to the type of fluid and to each gasconstituent and may have temperature dependency. Gas solubilitycoefficients can be used to relate the partial pressure of gas in thegas cell with the concentration of dissolved gas in oil. The extractedgases being in equilibrium with the dissolved gases in oil may providemore accurate readings without requiring precise knowledge of extractionrates. In some embodiments, the extraction probe 22 of the presentdisclosure may comprise at least one ring of highly gas permeable tubingthat is not permeable to liquid. In some embodiments, the extractionprobe 22 may be connected to a closed-circulation system. Theclosed-circulation system may include one or more pumps for gascirculation and a gas cell, for example, gas cell 26, for analyticalmeasurement of the gas.

The present disclosure includes devices, systems, and methods adapted tomonitor the health of a transformer by measuring dissolved gases withininsulating oil of the transformer. For example, the concentration ofspecific gases can give indications of specific aspects of the operationof the transformer. Direct oil sampling and analysis of dissolved gasescontained in transformer oil use active extraction of the gases andactive measurement techniques that consume the gases through theanalyses. They are often implemented by circulating and/or conditioningoil samples outside the transformer in an oil circuit and may present arisk of oil leakage in case of breakage of the oil circuit. By contrast,embodiments of the devices, systems, and methods of the presentdisclosure permit online measurement with high accuracy and withoutactive extraction. In some of the disclosed embodiments, oil containingthe dissolved gases is circulating around highly permeable material tubewithin a fluid chamber 46 communicating fluidly with the transformer 10through the pipe extension 42. In some embodiments, the oil circulationaround the permeable tube may be generated by pump, propeller and/orother mechanical systems and/or using thermally induced convection.Gases contained in oil can pass through permeable material to reach thegas phase loop. The permeable material properties can assist inobtaining equilibrium between gases in the liquid and gases in the gasphase loop. The gas loop may include a gas cell with optical inlet andoutlet allowing examination of the gases by optical analyzer.

Devices, systems, and methods of the present disclosure may includehighly permeable fluoropolymer tubing, such as Teflon AF family ofamorphous fluoroplastics, by way of example. Highly gas permeablematerial can promote gas equilibrium and can improve measurementresponse time. The tubing may be rolled to form one or more turns of acoil. Devices, systems, and methods of the present disclosure mayinclude circulation of the transformer fluid (e.g., oil) around thiscoil. A structural ring may support the tubing. According to the presentdisclosure, the fluoropolymer tubing may be connected to a gascirculating loop. The gas circulating loop may include one or more pumpsto enhance reliability. In some embodiments, stainless steel tubing maytransport gas to a gas cell for analysis. In some embodiments, aspectrometer may perform analysis of the gases. In some embodiments,in-oil sensors may be used for H₂ and/or H₂O measurement.

Devices, systems, and methods of the present disclosure may includepassive extraction of dissolved gases and measurement, in lieu of activeprinciples for gas separation and measurement. In some embodiments, thepresent disclosure may include transport of extracted gases without acarrier medium (e.g., a carrier gas). In some embodiments, a lowerpressure may be formed within the extraction probe 22, relative to thepressure within the gas cell 26 to assist with extraction of dissolvedgases.

Devices, systems, and methods of the present disclosure can be used intransformer monitoring and/or specifically in monitoring of dissolvedgases analysis in transformer fluid such as oil. For gas phase analysis,gases can be extracted from the transformer oil. Measurement of thegases can require a complex system for analysis, and in someembodiments, the gas sample can be transported to a gas analyzer. Thedevices, systems, and methods of the present disclosure can be helpfulin avoiding transporting the transformer oil itself to an analyzer,which can present a risk of oil leakage in case of tubing breakage.

Use of passive measurement and passive extraction of the gases cansimplify the calibration and installation of gas analysis systems. Useof high porosity and/or highly permeability material can help to reachequilibrium between gases in oil and gases in the sample gas phase.Using gases equilibrium, without requiring new gases to be sampled, canreduce risk of contamination of the oil. Use of a lower pressure(relative to the pressure within the gas cell) in the gas sampling probecan reduce the response time of the systems. The use of multipletransport pumps can help to reduce risk of failure. In some embodiments,measurement of H₂ may be conducted in gas phase to reduce the cost. Insome embodiments, measurement of O₂, H₂, and/or N₂ may be performedoptically and/or with non-optical sensors. In some embodiments, O₂ canbe measured by paramagnetic analyzer. In some embodiments, gas leakdetection may be performed by monitoring the presence of CO₂ or H₂O withthe gas cell, whether by direct and/or indirect sampling. The presentdisclosed devices, systems, and methods may involve advanced analysesand identification of interferent and outlier.

The present disclosure includes devices, systems, and methods for dualchannel optical gas analyzers for compensation of ambient airconstituents. Spectrometers can be used to measure light absorptionspectra of gases. When gases of interest in a sample under observationare also present in ambient air (e.g., air either in the analyzer and/oraround the sampling system) or when other gases in ambient air mightinterfere with the measurement of the gases of interest, spectrometersoften must be purged, for example, with a purified gas to determine thecontribution due to the absorption of only the gases of interest in thegas sample. The present disclosure includes devices, systems, andmethods to reduce and/or remove the need for conditioning of the air inthe analyzer or around the sampling system. The present disclosureincludes spectrometers with two measurement channels. One channel canreceive light propagating through ambient air and through a sampling gascell. The transmitted light is then detected by a photodetector whichgenerates an electrical signal that is digitized using an analog todigital converter. Another channel receives light propagating throughambient air only. Unlike in the first channel, the light of this secondchannel is not propagating through the sampling gas cell. The gasabsorption contribution to the transmitted light in this second channelis related to ambient air constituents. The transmitted light of thissecond channel is detected by a second photodetector which generates anelectrical signal that is digitized using a second analog to digitalconverter.

Devices, systems, and methods within the present disclosure may includelight sources that split the light (e.g., by beam splitter, lightdivider, and/or any other suitable light splitting technique), a gascell that may contain one or many gases of interest, components toinsert gases into the gas cell, a first detector measuring the lighttransmitted through the gas cell and through ambient air, a seconddetector measuring the light transmitted only through ambient air, aprocessor to determine the concentration of one or more gases present inthe sampling gas cell from the first channel signal, and removeinterferences and/or contribution of gases in ambient air of the firstchannel based on the ambient air signal recorded from the secondchannel.

In some embodiments, a light source may be modulated by aninterferometer. The light source may be divided in two different beamsby a 50/50 Wedged ZnSe Beamsplitter. One of the beams may propagatethrough the gas cell and may reach the gas cell detector. The other beammay be directed towards a reference detector, to sense the ambient aircomposition only. The propagation distance in ambient air can beadjusted for both beams. The adjustment can be performed in a mannersuch that both the light transmitted by the gas cell and reaching thefirst detector and the light reaching the reference detector of thesecond channel propagate through similar distances in ambient air. Insome embodiments, it may be assumed that ambient air composition in theinstrument is homogeneous, and the light absorption due to the gasesfrom ambient air should be the proportional to the gases concentrationas well as to the respective propagation distance of both channels.

In some embodiments, the gas cell may be a closed container with oneinlet and one outlet to fluidly connect to form a gas circulation loop.The light from the interferometer can enter the gas cell from one sideand exit through the other side to the gas cell detector. The gas cellcan be temperature controlled by a cartridge heater. The pressure andtemperature of the gases in the gas cell can be measured and used asinput parameters to the calculation of gases concentrations.

The present disclosure includes devices, systems, and methods in whichthe need for a purging system can be reduced and/or removed. Reducingand/or removing the need for a purging system can be an advantage whenan analyzer is located in remote areas and purging systems are notavailable and/or are costly to install and operate. Concentration ofgases in the gas cell that may also be present ambient air can bedetermined without purge, scrubber, desiccant and/or analyzer sealing.Other ambient air gases which have absorption signatures that mayinterfere with the determination of the gases concentration in the gascell may also be compensated without purge, scrubber, desiccant and/orsealing. With the teachings of the present disclosure, the gases inambient air can be measured simultaneously with the gases in the gascell if desired, as opposed to calibration methods where only onechannel can be used. Single channel calibration may perform referencebackground measurement taken apart from and/or without the gases ofinterest in the gas cell. The devices, systems, and methods of thepresent disclosure can provide an advantage when ambient air compositionvaries over time. The devices, systems, and methods of the presentdisclosure can include calibration for spectral intensity of the source,and calibration for the spectral characteristics of optical componentsthat are common to both the first and second channels.

The present disclosure can be used in the field of transformermonitoring by analysis of dissolved gases. The teachings of the presentdisclosure are generally applicable to other fields where opticalmethods require purge, scrubber, desiccant and/or sealing in order tocalibrate, remove, and/or correct for ambient air constituents. Thedevices, systems, and methods of the present disclosure can provide analternative to systems taking reference measurements using only onedetector, by removing the gases of interests from the gas cell and/orbypassing the gas cell.

Measuring low concentration gases by spectroscopy with accuracy can bechallenging, particularly when the same gases or other interfering gasesare present in ambient air, either in the analyzer or around thesampling system. Concentration of these gases in ambient air and/or therelative propagation distance of the light in ambient air could benon-negligible compared to the concentration of the gases in the gascell and the propagation distance in the gas cell. Furthermore, theconcentration of these gases in ambient air may vary with time, andunexpected gases can appear in ambient air in some sites. Pressure andtemperature of the ambient air may differ from the pressure andtemperature of the gas sample in the gas cell.

To remove the contribution of ambient air gases, analyzers are oftenpurged with purified gases (by way of example, the MB3000 spectrometermarketed by ABB Inc., includes a purging option). Purging can requirebottles of purified gases, like Nitrogen, and/or a purified gasgenerator. Purge air is often dried to remove humidity, which can be asignificant interferent in some instances, and CO₂ is often removed aswell with a scrubber. In other systems where a purge is not possibleand/or desirable, desiccants and/or scrubbers are used to removehumidity and/or other gases, but must be replaced or regenerated aftersome time. Other exemplary techniques can include moving relay mirrorsto the gas cell in and out of the first channel in order to bypass thegas cell and direct the light to the detector to take backgroundmeasurement. The relay optics can be designed such that the propagatingdistance in air with and without the relay optics is the same. Stillother exemplary techniques can include using a scrubber to remove thegas component of interest from the gas cell after measuring the gassample with the gas component of interest and inferring itsconcentration by the comparison of those two alternate measurements.Still other techniques may vary the pressure and/or the temperature ofthe gas sample to discriminate its composition over ambient aircomposition. In cases where the purge gas is supplied from anexhaustible source, such as a bottle, the exhaustible source will needto be refilled and/or changed at periodic maintenance intervals. Purgegenerators can be costly equipment that can require maintenance as well.Scrubbers and desiccants also require maintenance. Thus, the purge-basedsystems can increase the cost of operating spectrometers.

As mentioned above, the present disclosure can include reducing and/orremoving the need for a purging system, desiccants, scrubbers and/orinstrument sealing. Accordingly, the devices, systems, and methods ofthe present disclosure can reduce installation and/or maintenance costsrelated to the spectrometer, and can enable solutions for remote siteswhere purging systems are not available and/or maintenance cannot beperformed frequently due to cost and/or safety issues. In someembodiments, the devices, systems, and methods of the present disclosuredo not require moving optics and/or sample gas pressure modulation, andthe ambient air constituents can be measured simultaneously with the gascell constituents.

Since spectrometers using certain teachings of the present disclosurecan measure spectra of ambient air, they may also detect and/orcompensate for unexpected gases present in the ambient air, as opposedto scrubbers that are designed for specific constituents. Devices,systems, and methods of the present disclosure may be used to detectother defects around the transformer, for example but withoutlimitation, detection of insulation gas leaks, such as SF₆. By measuringand removing ambient air absorption, the devices, systems, and methodsof the present disclosure can reduce sensitivity to ambient aircompositions. The composition of the air inside the optical analyzerand/or around the sampling system may not need to be controlled by useof purge system, desiccants, scrubbers and/or instrument sealing.

In some embodiments, the devices, systems, and methods of the presentdisclosure may use factory calibration to characterize the difference oflight propagating distances in air between first and second channels. Insome embodiments, the devices, systems, and methods of the presentdisclosure may use factory calibration of the system to measure thespectral response of the first and second detectors as well as spectralresponse of optical components not common to first and second channel.In some embodiments, the devices, systems, and methods of the presentdisclosure may use factory calibration to characterize the spectralresponse and/or instrument line shape of the first and second channelsin order to improve the compensation of air constituents in the firstchannel using the second channel. Factory calibration may include purgeof the analyzer. The present disclosure include techniques developed toadjust the position of system components (mirrors, lenses, detectors,etc.) to minimize the difference of light propagating distance in airbetween first and second channel. In some embodiments, one or morealgorithms may be used to compensate for the ambient constituents of thefirst channel using the second channel signal.

While certain illustrative embodiments have been described in detail inthe figures and the foregoing description, such an illustration anddescription is to be considered as exemplary and not restrictive incharacter, it being understood that only illustrative embodiments havebeen shown and described and that all changes and modifications thatcome within the spirit of the disclosure are desired to be protected.There are a plurality of advantages of the present disclosure arisingfrom the various features of the methods, systems, and articlesdescribed herein. It will be noted that alternative embodiments of themethods, systems, and articles of the present disclosure may not includeall of the features described yet still benefit from at least some ofthe advantages of such features. Those of ordinary skill in the art mayreadily devise their own implementations of the methods, systems, andarticles that incorporate one or more of the features of the presentdisclosure.

1. A gas analysis device for determining characteristics of dissolvedgas of a transformer, the device comprising: a gas cell defining acavity for receiving gas for analysis, a light source arranged totransmit light, a cell light detector arranged to receive lightpropagated by the light source through the cavity of the gas cell, and areference light detector arranged to receive light propagated by thelight source through an ambient space.
 2. The gas analysis device ofclaim 1, wherein a cell light distance is defined between the cell lightsource and a reference source point of light from the light source. 3.The gas analysis device of claim 2, wherein the cell light distancecorresponds to a reference light distance defined between the referencesource point and the reference light detector.
 4. The gas analysisdevice of claim 3, wherein the reference source point is a beam splitterarranged to divide light from the light source into at least two beams,one of the at least two beams for propagation through the cavity andanother of the at least two beams for propagation through the ambientspace.
 5. The gas analysis device of claim 4, wherein the cell lightdetector is arranged to receive light from the beam propagated throughthe cavity that has not been absorbed by gas within the cavity, andwherein the reference light detector is arranged to receive light fromthe beam propagated through the ambient space that has not been absorbedby gas within the ambient space.
 6. The gas analysis device of claim 1,wherein each of the cell light detector and the reference light detectorprovide a signal indicating a spectrum corresponding to light receivedby that detector.
 7. A transformer comprising: at least one electricalwinding, a fluid system including fluid for insulating the at least oneelectrical winding, and a gas analysis system for determiningcharacteristics of gas dissolved in the fluid of the fluid system, thegas analysis system including an extraction probe having gas-permeablematerial for receiving dissolved gas from the fluid and a gas analyzerincluding at least two channels, wherein at least one of the at leasttwo channels is arranged to determine characteristics of gas extractedfrom the fluid.
 8. The transformer of claim 7, wherein at least one ofthe two channels is arranged to determine characteristics of ambientgas.
 9. The transformer of claim 7, wherein the at least two channelsare arranged to receive light propagated from the same light source. 10.The transformer of claim 7, wherein the at least one channel is arrangedto propagate light through a gas cell containing gas extracted from thefluid for reception by a cell detector of the at least one channel. 11.The transformer of claim 10, wherein a cell light distance is definedbetween a reference source point of light of the light source and thecell detector, and wherein the cell light distance corresponds to areference light distance defined between the reference source point anda reference detector of at least one other channel of the at least twochannels.
 12. The transformer of claim 11, wherein the reference sourcepoint includes a beam splitter arranged to divide light from the lightsource into at least two beams, one of the at least two beams forpropagation through the gas cell and another of the at least two beamsfor propagation through ambient space.
 13. The transformer of claim 12,wherein the cell light detector is arranged to receive light from thebeam propagated through the gas cell that has not been absorbed by gaswithin the gas cell, and wherein the reference light detector isarranged to receive light from the beam propagated through the ambientspace that has not been absorbed by gas within the ambient space. 14.The transformer of claim 13, wherein each of the cell detector and thereference detector provide a signal indicating a spectrum correspondingto light received by that detector.
 15. The transformer of claim 7,wherein the gas analyzer includes a gas cell fluidly connected with theextraction probe to form a gas circuit.
 16. The transformer of claim 7,wherein the extraction probe includes an extraction coil.
 17. Thetransformer of claim 16, wherein the extraction coil includes a numberof coil turns arranged in contact with the fluid.
 18. A transformercomprising: at least one electrical winding, a transformer fluid systemincluding fluid for insulating the at least one electrical winding, agas analysis system for determining characteristics of gas dissolved inthe fluid of the fluid system, the gas analysis system including anextraction probe having gas-permeable material for receiving dissolvedgas from the fluid and a gas analyzer including at least two channels,wherein at least one of the at least two channels is arranged todetermine characteristics of gas received from the fluid, and a gascircuit defined at least partially by the extraction probe and the gasanalyzer for circulating gas extracted from the fluid.
 19. Thetransformer of claim 18, wherein the gas analyzer includes a gas cellfluidly connected with the extraction probe to form the gas circuit. 20.The transformer of claim 18, wherein the gas analyzer propagates lightthrough gas within the gas cell for reception by a detector of the atleast one channel.